Ecology and conservation of food and medicinal plants

trade in MAPs from TMs and in markets, but it is difficult to estimate the value of this ‘hidden economy’. Experience from China, India and South Africa shows that sustainable harvesting is not sufficient to save threatened species, and in China and South Africa there are initiatives to cultivate MAPs. It is important to intensify studies on populations and sustainability of harvesting of medicinal plants in Tanzania. Sustainable harvesting and growing of medicinal plants have the potential of accelerating rural development. Some local stakeholders have already started a process that can contribute to this development. Pharmacological studies to confirm safety and effectiveness of medicinal plants are now being done, but still very few plants have been screened.

4.2.Ecology and conservation of food and medicinal plants 4.2.1. Germination and early seedling growth experiment

The aim of Paper II was to investigate the influence of light and temperature on the establishment of two Ugandan medicinal trees; Mitragyna rubrostipulata (Hallea

rubrostipulata), and Sarcocephalus latifolius. The trees are regarded as important in the local health system, are getting scarce in the areas of study and turned out to be problematic to grow in a field setting. In Gadumire, Kaliro we tried to sow in an experimental field, but did not succeed.

In Sango Bay a local nursery project tried to germinate M. rubrostipulata without success.

Seeds from the trees were collected in these two areas, dried and brought to Norway. We set up two experiments, one on germination conditions, and one on early seedling growth. Our main findings were that both species needed light to germinate; Mitragyna rubrostipulata had a temperature optimum of 25 qC with 79% germination, while the total germination after 28 days was close to 60% for temperatures between 20 and 35 qC for Sarcocephalus latifolius. Seedlings of M. rubrostipulata died at 35 qC, and seedlings of S. latifolius died at the low temperature of 15 qC (Fig. 1 and 2, Paper II). The temperature preferences of the two species reflect the temperature of their natural habitat. Both seeds and seedlings are very small for both species.

This may be one of the reasons why the seedlings had difficulties to establish. In the Sango Bay forest we could not see rejuvenation of M. rubrostipulata, and in the beginning the nursery group

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had problems germinating the seeds. It is possible that they covered the seeds with too much soil for them to germinate. In Kaliro reasons for failure may be predation or that the soil in the degraded area where we did the growing experiment was not able to retain water long enough for the seedlings to establish.

For both species, the seedlings had their best growth at 30 qC. Sarcocephalus latifolius had a much more rapid growth in the period of study. After 12 weeks, dry weight of shoots and roots of S. latifolius was almost 10 times higher than that of M. rubrostipulata (Fig. 3 and 4, Paper II).

However, we found a striking difference in the allocation of biomass to roots and shoots in the two species. While at the end of the experiment M. rubrostipulata had almost as much biomass in roots as in shoots, the allocation of biomass to shoots for S. latifolius was almost twice as high as to roots. This may be an adaptation by the Mitragyna seedlings to the oligotrophic

environment they grow in.

We concluded that nursery assistance is needed to establish healthy populations of the two species of study and probably many other endangered species.

4.2.2. Phenology and cultivation of some selected woody species

The aim of this study was to (1) gain knowledge about flowering and fruiting phenology and seed germination traits of selected medicinal trees, (2) to assess each species potential as a framework species, and (3) to find out if this method is suitable to conserve medicinal trees and the environment in Kaliro district, Uganda (Paper III).

4.2.2.1. Phenology

Phenology was performed in two areas: in Sango Bay the species Mitragyna (Hallea) rubrostipulata, Warburgia salutaris and Syzygium guinence, and in Kaliro District

Sarcocephalus latifolius, Securidaca longipedunculata, Capparis tomentosa and Psorospermum febrifugum was monitored for about one year (only data from the species that were included in the planting project is presented in the paper).

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We found that between December 2005 and December 2006 there were 2 fruiting periods for Mitragyna rubrostipulata, with peak flowering in January to February and a smaller flowering in May to June. Peak fruiting was in March and September. The flowering was in the dry season, and peak fruiting as the rain started. For Warburgia salutaris peak fruiting was recorded in September 2006 and March 2007, and for Syzygium guinense peak fruiting was found to be in July 2006.

In Kaliro we observed mature fruits on Sarcocephalus latifolius, Securidaca longipedunculata when we started registration in December 2006. For S. latifolius a new fruiting period started in February 2007, but the fruits took very long to mature, and peak fruiting was not until July/

August. S. longipedunculata had a new flowering period in April, but almost all flowers were destroyed by a hailstorm. P. febrifugum had long flowering (March-July) and fruiting (April-November) period, possibly because the birds ate the fruits as soon as they ripened. This fact also made it difficult for us to make seedlings from this species, as it was almost impossible to get ripe fruits. For Capparis tomentosa no flowers or fruits were recorded during the time of study.

4.2.2.2. The Framework species method

Field performance was assessed by monitoring survival, height and crown width once every month for 13 months after planting. Eleven species (Artocarpus heterophyllus, Calliandra calothyrsus, Callistemon citrinus Skeels, Carica papaya, Carissa spinarum L., Leucaena leucocephala, Markhamia lutea K.Shum., Sarcocephalus latifolius, Senna siamea (Lamarck) H.S.Irwin & Barneby, S. spectabilis (DC.) H.S.Irwin & Barneby and Terminalia schimperiana Hochst. ex Delile) proved to be excellent framework species. Eight species qualified as

‘acceptable’ FWS (Albizia coriaria Welw., Ceiba pentandra, Entada abyssinica Steud.,

Erythrina abyssinica Lam., Eugenia jambos L., Ficus sycomorus L., Maesopsis eminii Engl. and Milicia excelsa (Welw.) C.C.Berg),while seven species were ranked as ’marginally acceptable’

(Acacia macrothyrsa Harms, Calpurnia aurea Benth., Canarium schweinfurthii Engl., Capparis tomentosa, Ficus natalensis Hochst., Senna sp. and Warburgia salutaris). Annona squamosa Vell. was the only species rejected since both germination and survival was low. Whether the

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content of active compounds are as high in the cultivated, as in the wild growing plants, still need to be investigated. We believe that if they are planted in a mixed stand with mainly local trees, and without too much input of nutrients and water, it is likely that the content of active principles are close to the plant harvested in the wild.

We succeeded to cultivate two of five important medicinal woody species named by the traditional healers at the beginning of the study: Sarcocephalus latifolius and Capparis tomentosa. Securidaca longipedunculata we managed to germinate, but when the seedlings reached a certain size between 10 and 20 cm they started to wither. A few plants were planted in the plots, but none survived until the last monitoring. For Psorospermum febrifugum we did not manage to get ripe seeds because the birds were eating them, and for Maytenus senegalensis there were so few shrubs left in the area that we did not manage to get seeds at all. Zanthoxylum chalybeum is in great need of conservation measures, but this species also need further study.

Trees with good reaforestation traits could be recommended for planting while the species that were marginally acceptable or rejected require extra research since some of them are important medicinal woody species of conservation concern.